We propose to investigate the nutrient pathways of flexor tendons and flexor tendon grafts within the flexor sheath in chickens and monkeys by measuring the uptake of radioactive tritiated proline in (1) tendons detached from vascular connections but in contact with synovium, (2) tendons separated from the synovium but with unaltered vascular attachments, and (3) tendons attached by vascular attachments but surrounded by tissue culture synovium rather than the animal's own synovium. We also propose to use autoradiography to determine the pattern of distribution of radioactivity within the substance of the tendon and the rate at which nutrients diffuse along the course of the tendon. We propose to determine the metabolic rate at which tritiated proline is incorporated into tendon collagen by ethanol extraction of the radioactive amino acids of the various tendon preparations in vivo and in vitro at various time intervals. We propose to determine the radioactive uptake by tendon grafts with and without peripheral adhesions. We propose to determine the capacity of various tendon beds (i.e., synovial, synovectomized, and fibrous tubular sheath) to nourish tendon grafts.